Nephrin is a component of the slit diaphragm that bridges the filtration slits between adjacent podocyte foot processes. The gene for nephrin is mutated in congential nephrotic syndrome of the Finnish type. MAb 5-1-6 is a monoclonal antibody to the extracellular domain of nephrin that induces severe proteinuria in a complement independent fashion in a rat model. This model will be used to explore the role of nephrin in mainating glomerular permselectivity. Previous studies have demonstrated a link between nephrin and the actin cytoskeleton. This study will employ selective detergent extraction and differential centrifugation to determine whether the link between actin, nephrin and nephrin associated proteins (CD2AP, and podocin) is disrupted in this model. It will also be used to determine if there is any alteration of the distribution of nephrin or its associated proteins between the fraction of the protein found associated with the acitn cytoskeleton and that in detergent resistant membrane domains. Immunohistochemistry and electron microscopy will determine if there is a correlation with a change in the morphology of the slit diaphragm in this disease state.